1. Field of the Invention
This invention relates generally to M-16 and AR-15 rifle-platform firearms having improved direct-drive systems rather than impingement systems; and to retrofit kits which can be used to convert M-16 and AR-15 rifle-platform firearms to direct-drive systems, and the method of using such kits to retrofit M-16 and AR-15 rifle-platform firearms.
2. Description of the Related Art
Replacing the impingement system of the M-16 or AR-15 is not a new idea. Many attempts have been made to do so. It is well known to the gun industry and users of this rifle that it is prone to fouling and jamming due to its design which directs the discharge gas into the bolt carrier to activate the bolt and discharge the spent shell.
The disadvantages of the OEM impingement system are well known and are primarily due to hot, carbon-laden exhaust gases being directed into the bolt carrier and receiver. The heat alone tends to wear parts down, by among other things, exposing this area to thermal cycling. The soot or carbon from the expelled gases, expose the moving parts within the bolt carrier to a hostile environment. The oil needed to keep the area well-lubricated serves to exacerbate the problem by trapping particles and carbon. The combination of factors causes the parts to break, wear, or fail to operate. Failure to operate can be caused by, among other things, fouling and wearing of gas rings and the loosening of ejector and extractor springs. As a result, the spent shell is not ejected properly and the bolt carrier is prevented from traveling properly within the receiver. With extreme fouling and increases in temperature, the spent shell can become entrapped and the gas tube can melt, causing a restriction of flow to the bolt carrier and subsequent failure of operation. Thus, in order to ensure the proper operation of the rifle, it must be cleaned and continually lubricated. Such extra attention is a burden in the field, where reliable, trouble-free operation is essential. With many parts to keep track of, consistent cleaning is more difficult in the field.
Others have developed systems to replace the OEM impingement system. Some require that significant portions of the rifle be modified or replaced, such as the barrel and parts within the receiver. However, these systems have significant drawbacks. The cost of replacing the barrel and other parts is substantial. Furthermore, if machining is required to install the system, the user must send the rifle to a machinist to be modified, adding time and expense to the process, and potentially introducing error with each machining process.
Some manufacturers, such as Land Warfare Resources Corporation (LWRC), have designed systems that do not require the replacement of the barrel. The problems with such systems it that in order to clean or inspect the firearm, it is necessary to substantially disassemble a substantial portion of the system in order to access the rod assembly or the gas plug located in the gas block. In some cases, it is necessary to remove the hand guard and loosen the gas block, sliding it muzzleward so that the gas plug can be removed and the rod assembly is free and accessible. Many existing systems also segment the rod into several sections, so that the assembly can be removed from the tight quarters beneath the hand guard. For this reason, a single piece or continuous rod is not possible in such a system. A single rod would not have the necessary clearance for removal.
What is needed and not heretofore provided by the existing art is a M-16 and AR-15 rifle-platform firearm having a direct-drive system which does not require extensive disassembly of the system in order to clean or inspect the fire arm. Further, there is a need for a retrofit kits which can be used to convert M-16 and AR-15 rifle-platform firearms to direct-drive systems. Further needed is a retrofit system not requiring machined modification or replacement of the barrel and other primary parts of the rifle. What is further needed is a retrofit system that is easily assembled and disassembled in the field, having minimal complexity and minimal number of components. What is again needed is a retrofit system that can be removed for inspection and cleaning without substantial disassembly or removal of neighboring parts, such as the gas block or hand guard.